Method of manufacturing an electrical component, e.g. a digital contacting encoder

ABSTRACT

A rotary digital contacting encoder (FIG. 1) including a base (5), comprising--a base epoxy disk (501) with three external, pre-molded in place, connector pins (P 1  -P 3 ) on its exterior side extending through it, and a conductive layer in the form of two concentric layer rings (502 &amp; 503; FIG. 4); and--an encoder element made of a &#34;Kapton&#34; insulating substrate (510) carrying two, like concentric cog rings (511A &amp; 511B; FIGS. 3 &amp; 7) on its top side. Conductive vias (512 &amp; 513) electrically interconnect each respective cog ring with its respective conductive layer ring and its respective external connector pin, the vias forming conductive paths through the insulating substrate between the conductive layer and the cog rings. The presence of the conductive layer 502/503, which can be screen printed on the base disk, greatly simplifies the relative alignment of the encoder element, conductor pads and terminals. Using the conductive layer the encoder element can be positioned at almost any angular location, while still obtaining proper electrical contact with the terminal pins.

REFERENCE TO RELATED APPLICATIONS

The application relates to some of the same subject matter as assignee's applications: application Ser. No. 07/264,588 filed Oct. 31, 1988, entitled "Precision Resistance Film and Terminating Method and Product"issued as U.S. Pat. No. 4,845,839 on July 11, 1989 and application Ser. No. 07/330,016 filed on even date herewith by the same inventors entitled "Electrical Interconnect Substrate Design & Method With Interconnecting Vias for Digital Encoders and the Like;"

the disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the design and manufacture of electrical components, such as, for example, digital contacting encoders or pulse generators and the like, whether linearly or rotatably moved. Additional examples of other electrical components, besides rotary and linear encoders, which could benefit from the use of the present invention include potentiometers, position sensors, variable resistors, switching systems, magneto-resistive devices, etc. More particularly the present invention relates to an electrical interconnect substrate design for such electrical components, which allows for greater ease in manufacture of the device.

BACKGROUND ART

Rotary digital contacting encoders or rotary pulse generators are known, in which a cog-type conductive pattern is provided on an insulating substrate, to which three external electrical connections are selectively made and over which a "U" shaped, bridging, wiping contact is rotated. As the "U" shaped contact is rotated, it alternately connects a common pin or connection (for example, pin "2") for a limited period of time to one and then the other of the other two connections (namely, the remaining pins "1" & "3"), alternately and sequentially making bridging interconnection between the common pin and one of the other pins, producing digital-type, pulsed electrical signals across the pins, having the wave forms shown in FIG. 8 hereof.

The cog pattern in such devices typically includes two, concentric cog rings with generally opposed, alternating cogs, as shown in detail in FIG. 7 hereof, and are quite small and fine in their design. They involve gaps between the generally opposed, radially extended cogs of, for example, only fifty-five ten-thousandths (0.0055") of an inch with a ring width of, for example, only thirty-nine thousandths (0.0039") of an inch.

The cogs of the rings are either directly opposed, as, for example, is shown in U.S. Pat. No. 4,443,670 of Nakamura et al issued Apr. 17, 1984, or somewhat staggered or axially off-set, as shown in FIG. 7 hereof.

In the manufacture of such devices in the prior art, the electrical connections to the concentric rings were directly made to them, usually peripherally as shown in the '670 patent, resulting in the need for relatively precise alignment and positioning of the electrical connections with the rings, with very little tolerance being allowed, causing manufacturing problems and difficulties.

The present invention is designed to avoid these manufacturing problems and difficulties.

DISCLOSURE OF INVENTION

Thus, the present invention is directed to the design and manufacturing of various electrical components, such as, for example, a rotary digital contacting encoder or pulse generator, or other like components, which design and manufacturing methodology avoids the precise positioning and alignment requirement for the external electrical connections with the cog rings or other electrical signal affecting strips, as required in the prior art.

The present invention achieves these objectives by providing in, for example, the exemplary embodiment, a circumferentially extended, circular conductive layer in the form of two concentric rings on a base, which layer ultimately is used to carry the cog pattern, the presence of which conductive layer allows great latitude in the positioning and alignment of the electrical connections with the cog rings.

For example, the exemplary embodiment hereof allows the positioning of the alternate signal pin connections anywhere along three-hundred-and-forty (340°) degrees of the circumference of the cog rings and a tolerance of, for example, twenty to thirty thousandths (0.020-0.030") of an inch placement in the "x & y" directions and still achieve reliable and accurate electrical interconnections to the rings.

In the exemplary embodiment, which includes having the conductive cog pattern made on an electrically insulating substrate of, for example, Dupont's "Kapton", a conductive silver layer is provided, for example, by being screen printed, on a base of, for example, molded epoxy. The conductive layer includes two concentric rings, following the general configurations and alignment of the concentric cog rings.

If it is desired to have the ring pins lie on the periphery of the same circle, one of the concentric rings of the conductive layer is gapped, and the other concentric ring includes a radially extended leg projecting into the gap. If the ring pins can be radially off-set with respect to one another, two complete, concentric circles can be used for the conductive layer.

In the exemplary embodiment described in detail below a molded epoxy base provides an external wall through which three, externally extended, orthogonal pins make electrical connection to the device's internal electrical components, two of which are made to the concentric cog rings. The cog pattern on the "Kapton" substrate is positioned on the epoxy base, with the ring pins making electrical contact with the rings through, for example, conductive vias, one within the gap through the radially extended leg of the outer ring in the silver layer and the other through the inner conductive ring layer.

If the cog pattern is positioned on an insulating substrate, the final interconnection of the conductive layer rings with the cog rings on the insulating substrate can be made by providing, for example, relatively small holes or via openings through the substrate and filling the holes or via openings with conductive material, in accordance with the teachings of the co-pending concurrently filed application Serial No. 07/330,016 referred to above.

Applications for the exemplary finished digital contacting encoder of the present invention include, for example, the home satellite dish market and various electronic instruments, etc.

The digital contacting encoder of the present invention can be substantially smaller and more rugged than other comparable products on the market. Despite its sturdy design, the unit can be made to weigh, for example, only a half an ounce (0.5 oz.) with exceptionally efficient operation and with rotational life rated in excess of, for example, two hundred thousand (200,000) shaft revolutions.

Additional examples of other electrical components which could benefit from the use of the present invention include, in addition to encoders (both rotary and linear), potentiometers, position sensors, variable resistors, switching systems, magneto-resistive devices, etc.

Typically, each of these components will include:

a rigid base having an exterior side and an interior side;

at least two, externally exposed electrical contacts on the exterior side of the base, one of them being a common contact and the other being a strip contact for connecting a strip of conductive material within the component into an external circuit;,

an electrical signal varying element, including--

a relatively rigid substrate, which typically but not necessarily is made of insulating material, and has a top side and an underside, and

at least one, longitudinally extended strip of signal affecting, conductive material located on the top side of the substrate; and

a movable, bridging member electrically connected to the common contact and associated with the strip, movably sweeping along the strip causing an electrical signal imposed across the common contact and the strip contact to vary due to the changing relative position of the bridging member with respect to the length of the longitudinally extended strip.

The foregoing and other features and advantages of the present invention will become more apparent from the following further description and its related drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded, perspective view of an exemplary rotary digital contacting encoder with the electrical interconnect substrate design of the present invention, with the upper substrate section and the housing section turned inwardly toward the viewer to show the internal structure of the encoder; while

FIGS. 2A & 2B are front and rear views, respectively, of the exemplary encoder of FIG. 1.

FIGS. 3, 4 & 5 are plan views to similar scale of the associated cog rings, supplemental conductive layer rings and rear end, respectively, of the encoder of FIG. 1, the conductive layer rings of FIG. 4 being provided in accordance with the teachings of the present invention; with FIG. 5 being substantively identical to FIG. 2A but to a different scale.

FIG. 6 is an exploded, side perspective view of the encoder element, including the cog pattern and its substrate, and the epoxy base and its conductive layer for the encoder of FIG. 1, with the conductive layer being provided in accordance with the teachings of the present invention.

FIG. 7 is a plan, detail, close-up view of the exemplary cog pattern of FIG. 3 but with the former being taken from the opposite side of the latter.

FIG. 8 is a wave form diagram illustrating the digital-type pulses generated across pins "1" & "2" and pins "1" & "3" of the exemplary encoder of FIG. 1.

FIG. 9 is a flow chart diagram illustrating the exemplary manufacturing methodology of the present invention for making the exemplary encoder of FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION Structure & Operation of Encoder

With reference to FIG. 1, the exemplary rotary digital contacting encoder or pulse generator includes a shaft 1 and a cylindrical housing 2, in which the rotation of the shaft causes the internal "U" shaped wiping bridging contact 3 on base 4 to rotate. A bottom or rear base 5, carrying a conductive cog pattern, is affixed to the housing 2 with, for example, an adhesive, so that, as shaft is rotated, the "U" shaped contact is wiped across the fixed cog pattern, alternatively bridging the common pin P₂ across opposed, juxtaposed ones of the cogs, as explained more fully below.

The "U" shaped contact 3 includes two, extended, parallel, resilient arms 3A & 3B, with the arm 3A always being in electrical contact or connection with the common external connection pin P₂, which is centrally located in the center "C" of the bottom base 5. The arm 3B on the other hand is positioned to be wiped across the central area "CA" of the two opposed cog rings, bridging across the then contacted one of the radially extended, opposed cogs to the center area "C", alternately connecting the inner and outer cog rings electrically to the center or reference pin P₂, to which rings the other pins P₁ & P₃ are electrically connected, as explained more fully below.

The wiper contact arm 3B terminates in at least two or more sub-arms or fingers, which are laterally spaced from one another, with the inner-most one (as viewed from the perspective of FIG. 1) sweeping across the cogs of the inner cog ring 511B and the outer-most one sweeping across the cogs of the outer ring 511A.

As can be seen in FIG. 2A, the front of the housing 2 includes a sleeve 7, through which the shaft 1 passes. The outer surface of the sleeve 7 typically would be threaded for connecting the housing 2 to a surface with a nut. The front of the housing 2 also includes an orthogonally extended, male positioning pin 6, which allows the housing to be mounted onto, for example, the back-side of a panel (not illustrated) with a desired angular alignment, with the male pin 6 being mated with an appropriately positioned female orifice in the panel, while the sleeve 7 would extend through a hole in the panel to be affixed with a nut on the other side. Appropriate connection would then be made to the shaft 1 to cause it to be rotated.

As seen in FIGS. 2B & 6, the rear end of the base 5 includes three, orthogonally extended external pins or contacts P₁ -P₃ for connecting the encoder into a circuit external to the encoder. The external circuit typically would include a reference or power DC voltage supply of, for example, five volts. As shaft is rotated in a clockwise ("CW") direction, the circuit in conjunction with the encoder element produces the digital-type, pulsed wave forms as illustrated in FIG. 8 as channels "A" & "B" at the cog pins P₁ & P₃. This is caused by the action of the wiping contact arm 3B alternately switching in and out a cog from one ring and then the other ring and cyclically back and forth with respect to the DC powered central pin P₂.

The encoder element, comprising the cog pattern created by the two longitudinally extended, cog rings or strips 511A & 511B, on the substrate 510, thus serves as a signal varying element, with the relative position of the movable contact arm or bridging member 3B with respect to the cog rings, affecting the signal "seen" at the external ring or strip pins P₁ & P₃, as the current alternately flows through the conductive material of the strips.

Thus, for example, cog C-A of the outer cog ring 511A (note FIG. 7) is switched into the power circuit and then cog C-B from the concentric inner ring 511B is switched into the power circuit, and then outer cog C-C, and so forth, during the rotation of the shaft 1, producing the pulsed signals in the two channels "A" & "B".

It is noted that the cogs of the outer ring 511A are phase shifted or angularly off-set with respect to the cogs of the inner ring 511B and that the three sub-arms or fingers of the wiping contact arm 3B are skewed in that they do not lie in the same radial line as they are swept across the central area "CA" of the cog rings 511A & 511B. As a result, there is a phase difference between the pulsed signals, as illustrated in FIG. 8. If desired, the parts could be arranged and designed, so that no two cogs are ever simultaneously connected to the central pin P₂.

In the exemplary embodiment illustrated, it is desirable to have the ring pins P₁ & P₃ lie on the periphery of the same circle, coincident with the inner cog ring 511B and that defined by the inner conductive layer ring 502 (note particularly FIG. 6). Accordingly, as can be seen in FIG. 4, the conductive layer on the base 5 is provided in the form of two concentric circles, the inner one (502) of which includes a gap 504, into which a radially extended leg 505 from the outer ring 503 extends, to which is connected the ring pin P₃. The gap 504 and the connecting leg 505 are positioned to coincide with the hole in the epoxy disk 501 forming the base 5 into which the P₃ (or, alternatively, the ring pin P₁) is placed (note FIGS. 5 & 6).

For better visualization of how the external connecting pins P₁ -P₃, the concentric, conductive layer rings 502 & 503 and the concentric cog rings 511B & 511A are respectively associated together, it is noted that FIGS. 3-5 are substantially to the same relative scale.

To achieve electrical interconnection between the concentric, conductive layer rings 502 & 503 and the concentric cog rings 511B & 511A through the insulating substrate 510, which can be made of, for example, Dupont's "Kapton," conductive vias or tunnels 512 & 513, respectively, are formed between them through the insulating substrate 510, as described more fully in the concurrently filed application Ser. No. 07/330,016 referred to above and generally indicated in FIGS. 3 & 6 (note via holes 516 in the latter).

On the other hand, if the substrate 510 was not of an electrically insulating or non-conductive material, via tunnels would not be necessary. If such was desired, the cog pattern or strips could be formed from sufficiently thick and strong conductive material(s), that would inherently have built in to them their own "substrate(s)," it then only being necessary to electrically isolate the two cog rings or strips, if multiple strips are needed, as for example for the two cog ring/two strip or ring pin encoder illustrated.

Method of Manufacture of Encoder

To manufacture the bottom base 5, which includes the cog rings 511A & 511B, the insulating substrate 510, the conductive layer rings 502 & 503 and the epoxy base 501, the following exemplary method, summarized in the flow chart of FIG. 9, can be used.

To form the cog/substrate encoder element, a sheet or film of plain "Kapton," which is made of a polyimide resin, may be used as the substrate 510. A copper or other conductive layer is deposited onto the top side of the "Kapton" substrate, from which layer the cog rings 511A & 511B ultimately will be formed. If so desired, a gold plate layer can be added on top of the copper layer for enhanced conductivity.

A layer of photo-resist material is applied over the copper layer and exposed and developed to form the pattern of the cog rings 511A & 511B. The copper layer is then photo etched, leaving the copper in the pattern of the cog rings 511A & 511B on the top side of the "Kapton" substrate, forming the encoder element of the device. Circular cuts are then made through the substrate by stamping or die cut, forming the cog/substrate 510/511A-B, in the form illustrated in FIGS. 6 & 7.

Either before or after making the stamping cuts, conductive vias 512 & 513 are formed through the "Kapton" substrate 510, using the teachings of the concurrently filed application. For example, the "Kapton" material can be chemically etched away at the desired locations of the vias 512 & 513 producing the via holes 516 through the substrate to the cog rings, and the etched out areas filled with, for example, a silver epoxy.

It should be understood that, when the substrate is made of insulating material, the vias 512, 513 establish the final link in the conductive path from the cog ring 511A/511B through the insulating substrate 510 and its respective conductive ring layer 503/502 and its respective ring pin P₁ /P₃ and attain electrical continuity between the conductor cog patterns 511 and the encoder element mounting surface on the underside of the "Kapton" layer or film 510.

It should be further understood that, within the device, there is only one conductive path between each strip 511B/511A of the cog pattern and its respective ring or strip contact or pin P₁ /P₃ and that is through its respective conductive layer ring or strip 502/503. Thus, the conductive layer provides a serial link in the only conductive path from each of the external contact pins to its respective signal affecting strip.

To form the epoxy disk 501 with the conductive layer rings 502/503 on its interior side, the epoxy disk 501 is initially molded in the desired form with three holes through it to accommodate the external pins P₁ -P₃ and preferably the pins pre-molded in place extending through the thickness of the disk to terminate substantially co-planar with the interior surface of the base disk. The conductive layer in the form of the concentric rings 502 & 503 are then preferably screen printed on the interior side of the disk 501, with the gap 504 and the connecting arm 505 positioned over one of the ring pin holes for either the pin P₁ or P₃, and with the radius of the inner and outer concentric rings 502/511B and 503/511A being substantially coincident. When the pins are pre-molded into the base disk 501, the conductive layer is printed on the base disk, so that the radially extending arm 505 and the gap 504 coincide with the terminus of the selected ring pin (e.g. pin P₃ as illustrated in FIG. 6).

The conductive layer rings are concentrically spaced and electrically isolated from one another, with the inner, peripheral edge 502A of the inner ring 502 preferably extending past the inner peripheral edge 511B' of the inner cog ring 511B, and likewise with respect to the outer peripheral edges 503A/511A' of the outer rings 503/511A, as can be seen in FIG. 1. Thus, the radial extent or effective width of the combined conductive layer rings 502 & 503 is greater than the combined radial extent or effective width of the combined cog rings 511A 511B. This greater, relative extent or width adds to the allowable manufacturing tolerance with the interconnect substrate or base design of the present invention.

An exemplary material for the screen printing of the conductive layer for the conductive layer rings is a silver powder in an organic resin with solvents. The screen printed, conductive layer rings 502/503 provide separate conductive paths between each via and its respective cog ring, and its respective ring pin.

Besides screen printing for providing the conductive layer rings 502/503 on the base 501, evaporating or sputtering could be used, but screen printing is currently preferred for cost reasons. An exemplary thickness for the screen printed layer is twelve to thirty-five (12-35) micrometers or microns. In place of using the silver powder in an organic resin with solvents, exemplary alternate materials are gold, palladium, silver or copper, etc.

The presence of the conductive layer 502/503 greatly simplifies the alignment of the encoder element, conductor pads and terminals. Using the conductive layer 502/503, the encoder element can be positioned at almost any angular location, when bringing them together in preparation for joining the encoder element to the base, while still obtaining proper electrical contact with the terminal or ring pins P₁ & P₃.

In joining and bonding the cog/substrate 510/511 to the base 501 with the conductive layer rings 502 & 503 at the underside of the substrate 510 between it and the base disk 501, a non-conductive, transfer adhesive is provided on the underside of the "Kapton" substrate 510. An exemplary adhesive for joining the two sections or sub-elements together is a preform cut from a "B" epoxy.

The two sections or elements are then joined and bonded together using the adhesive to affix them with the longitudinally extended, concentric cog rings or strips in at least general alignment and substantially parallel with the longitudinally extended, conductive layer rings.

The electrical contact pins P₁ -P₃ are attached to the disk 501 by, for example welding, making sure that the concentric conductive layer rings 502/503 will make good electrical contact with their respective ring pins P₁ & P₃. Alternatively and preferably, the three pins P₁ -P₃ could be molded in place during the initial molding of the disk 501.

The foregoing methodology utilizes tape automated bonding (TAB) in a continuous process, and reference is had to co-pending application Ser. No. 07/264,588 now U.S. Pat. No. 4,845,839 referred to above.

The final assembly with the housing 2 and its shaft 1 and bridging contractor arm 3 can be completed manually with small tools and holding fixtures, or easily automated, as may be desired.

Although this invention has been shown and described with respect to a detailed, exemplary embodiment thereof, it should be understood by those skilled int he art that various changes in application, form, detail, methodology and/or approach may be made without departing from the spirit and scope of this invention.

For example, if the encoder were linear rather than rotary, the cog rings and conductive layer rings or strips would be in the form of longitudinally extended, straight, parallel strips rather than concentrically curved strips in the form of the circular rings illustrated. If the electrical component was a variable resistor with, for example, two pins, rather than the three pins for the encoder illustrated, rather than two sets of concentric ring pairs, only one set would be necessary, and, as before with respect to a linear encoder, the set could either be longitudinally extended in a straight line or curved, if rotary. In such an instance, the cogs of the longitudinally extended, straight strip could be said to laterally extend from the strip and be longitudinally spaced. For purposes of this application, it should be understood that the phrases "laterally extended cog" or "longitudinally spaced cogs" should be read to cover generically both the cogs as extending from either a longitudinally extended, straight strip or a curved strip; i.e., the cogs of a curved, ring cog pattern could be considered to be "laterally extended" and "longitudinally spaced" for purposes of this application. Likewise, the term "longitudinally extended" strip or layer should be considered to include both a strip or layer laid out in a straight line or in a curved or circular line. The foregoing is of course only exemplary of the changes in detail that would be necessary, as the principles of the present invention are applied to other forms of electrical components, besides the exemplary rotary encoder detailed above. 

Having thus described at least one exemplary embodiment of the invention, that which is new and desired to be secured by Letters Patent is claimed below.
 1. A method of manufacturing an electrical component which component includesa rigid base having an exterior side and an interior side; at least two, externally exposed electrical contacts on the exterior side of said base, one of them being a common contact and the other being a strip contact; an electrical signal varying element, includinga relatively rigid substrate having a top side and an underside, and at least one, longitudinally extended strip of signal affecting, conductive material located on the top side of said substrate; a movable, bridging member electrically connected to said common contact and associated with said strip, movably sweeping along said strip causing an electrical signal imposed across said common contact and said strip contact to vary due to the changing relative position of said bridging member with respect to the length of said longitudinally extended strip;comprising the steps of: (a) forming a longitudinally extended, affixed conductive layer on the interior side of said base in physical and electrical connection with said strip contact, with said conductive layer providing a serial link in said conductive path, the presence of said conductive layer allowing greater tolerance in positioning said strip in relation to said strip contact; (b) interfacing said conductive layer to the underside of said substrate, with the conductive layer located between said substrate and said base substantially coincident in alignment with said longitudinally extended strip, so that said conductive layer is electrically connected with said strip and said strip contact, and so that there is only one conductive path from said external strip contact to said strip within the component, the presence of said conductive layer allowing relatively great latitude in the alignment and placement of said strip with respect to said external strip contact; and (c) joining said substrate and said base together and using said conductive layer so that said conductive layer provides a serial link in the only conductive path from said external strip contact to said strip.
 2. The method of claim 1, wherein there is included the steps of:forming the strip on the substrate and the conductive layer on the base in two separate operations; generally aligning the substrate with the base, placing the underside of the substrate against the conductive layer; and bonding the substrate to said base.
 3. The method of claim 2, wherein there is included the steps of:providing a non-conductive adhesive between the electrical signal varying element and the base with the conductive layer on it; and bonding the signal varying element to the base with the longitudinally extended strip in at least general alignment with the longitudinally extended conductive layer, bonding the conductive layer to the substrate.
 4. The method of claim 1, wherein there is included the step of:making the base out of molded conductive plastic with the external contacts molded in place with the common contact located in the center of said base.
 5. The method of claim 4, wherein there is included the steps of:providing at least three external contacts on said base, with two of them being strip contacts, and providing at least two of said longitudinally extended strips on said substrate, said component being a rotary component; making the base out of molded conductive plastic with the external contacts molded in place with the contacts extending through the base, and with the common contact located in the center of said base and the strip contacts being spaced from one another and positioned away from the center of the base but lying on the periphery of the same circle; and providing the conductive layer in the form of longitudinally extended, parallel, layer strips on the interior side of the base in the form of concentric circles, with one having a gap along its circular length and the other having a radially extending arm extending into the gap, with the gap and arm coinciding with the interior terminus of one of said strip contacts.
 6. The method of claim 1, wherein there is included in step "a" the step of:screen printing the conductive layer on said base.
 7. The method of claim 1, wherein there is included in step "a" the step of:forming the conductive layer on said base with a width greater than the width of said strip, the conductive layer extending laterally past both sides of said strip when said substrate and said base are joined together. 